Radiation-emitting devices are generally known and used for radiation therapy in the treatment of patients, for example. Typically, a radiation therapy device includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high-energy radiation beam for therapy. This high radiation beam can be an electron radiation or photon (X-ray) beam. During treatment, the radiation beam is provided on one zone of a patient lying in the isocenter of gantry rotation.
The goal of radiation treatment planning is to maximize the dose to the target volume while protecting radiation sensitive healthy tissue.
A feature of radiation therapy involves portal images, which are commonly used in radiation therapy to verify and record the patient tumor location. Portal images, i.e., images of the port through the patient through which radiation emerges, include manual (film) and electronic images (EPI) taken before or after the treatment. Electronic portal images (EPI), when taken before the treatment, give the therapist the opportunity of correcting for minor patient positioning errors. Further, EPI allows therapists to take images remotely without going inside the treatment room.
Current technology using electronic imagers generally provides poor quality images, which limits the ability to have electronic images replace film images of the portal radiation field. The poor quality is due in part to the low light levels used in the video detection of the portal radiation image (e.g., brightness levels of less than 1 lux). The low light levels result in very low signal to noise ratio images. While manual parameter adjustments of the portal imaging device may be attempted to improve image quality, these manual adjustments often introduce unacceptable time delays in patient treatment. Furthermore, more dose than necessary is typically used as a result of the indeterminate manner of delivering an amount of radiation to form the image, where a therapist relies largely on intuition to estimate how much radiation to use to obtain a properly exposed image.
Accordingly, what is needed is a method and system for automation of controlling portal image acquisition so as to maximize signal to noise ratio in the electronic image and automatically capture the EPI.